首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 0 毫秒
1.
    
The origin of hysteresis behavior is probed in perovskite solar cells (PSCs) with simultaneous measurements of cell open circuit voltage (Voc) and photoluminescence intensity over time following illumination of the cell. It is shown, for the first time, that the transient changes in terminal voltage and luminescent intensity do not follow the relationship that would be predicted by the generalized Plank radiation law. A mechanism is proposed based on the presence of a resistive barrier to majority carrier flow at the interface between the perovskite film and the electron or hole transport layer, in combination with significant interface recombination. This results in a decoupling of the internal quasi‐Fermi level separation and the externally measured voltage. A simple numerical model is used to provide in‐principle validation for the proposed mechanism and it is confirmed that mobile ionic species are a likely candidate for creating the time‐varying majority carrier bottleneck by its reduced conductivity. The findings show that the Voc of PSCs may be lower than the limit imposed by the cell luminescence efficiency, even under steady‐state conditions.  相似文献   

2.
掺杂改性对钙钛矿晶体结构演化以及薄膜的光吸收性能有很大影响,并直接决定了钙钛矿太阳能电池的性能。采用一步溶液法制备了钙钛矿太阳能电池器件,分别研究了阳离子掺杂对钙钛矿晶体结构、晶体缺陷与器件光电性能的影响。研究表明,甲脒基(FA)及Cs离子掺杂改善了钙钛矿的成膜性以及薄膜的表面形貌。同时,阳离子掺杂有效降低了钙钛矿晶体的缺陷密度,这源于FA及Cs离子的取代掺杂有效促进了钙钛矿相的形成,避免了二次相的产生,并因此改善了钙钛矿薄膜表面形貌。器件的光电转化效率由10.29%提升至12.49%。  相似文献   

3.
    
In the landscape of photovoltaic research, carbon-based perovskite solar cells (C-PSCs) have attracted widespread attention due to their outstanding stability. However, compared to metal-based PSCs, their power conversion efficiency (PCE) lags markedly behind. The key lies in two primary factors: First, the inefficiency of the carbon electrode in transporting and collecting carriers; second, the energy level mismatch with adjacent functional layers. These problems increase both the charge transport resistance and the charge injection barriers, thereby diminishing the overall efficiency of the device. In this study, an effective strategy is presented to tackle this issue by developing modular C-PSCs that utilize dual carbon electrodes and implement multiscale modulation. This approach specifically focuses on three crucial aspects: establishing a highly conductive network, ensuring sufficient interfacial contact, and achieving well-matched energy band alignment. By synergistically incorporating 0D carbon black (CB) and 1D carbon nanotube (CNT) into dual carbon electrodes, a resilient conductive network with enhanced interfacial contact is established, creating favorable conditions for efficient carrier transfer. Additionally, the energy level structure of CB is meticulously adjusted at the molecular scale by introducing individually adsorbed titanium (Ti) atoms, effectively addressing the energy level mismatch with the hole transport layer (spiro-OMeTAD), and notably reducing the charge injection barrier at the interface. Based on the above strategy, the PCE of the C-PSCs has undergone a remarkable enhancement from 15.27% to 22.45%. Moreover, the device shows excellent stability, with its PCE retaining over 95% of the initial value even after 1000 h of continuous operation under one-sun intensity.  相似文献   

4.
    
Organic–inorganic hybrid perovskite solar cells are attracting the attention of researchers owing to the high level of performance they exhibit in photovoltaic device applications. However, the attainment of an even higher level of performance is hindered by their anomalous current–voltage (I–V) hysteresis behavior. Even though experimental and theoretical studies have suggested that the perovskite materials may have a ferroelectric nature, it is still far from being fully understood. In this study, the origin of the hysteresis behavior in CH3NH3PbI3 perovskite thin films is investigated. The behavior of ferroelectricity using piezoresponse force microscopy is first examined. Then, by comparing the scan‐rate‐dependent nano/macroscopic I–V curves, it is found that ion migration assisted by the grain boundaries is a dominant origin of I–V hysteresis from a macroscopic viewpoint. Consequently, the observations suggest that, even though ferroelectricity exists in the CH3NH3PbI3 perovskite materials, ion migration primarily contributes to the macroscopic I–V hysteresis. The presented results can provide fundamental guidelines to the resolution of hysteresis issues in organic–inorganic hybrid perovskite materials.  相似文献   

5.
    
Rapid extraction of photogenerated charge carriers is essential to achieve high efficiencies with perovskite solar cells (PSCs). Here, a new mesoscopic architecture as electron‐selective contact for PSCs featuring 40 nm sized TiO2 beads endowed with mesopores of a few nanometer diameters is introduced. The bimodal pore distribution inherent to these films produces a very large contact area of 200 m2 g?1 whose access by the perovskite light absorber is facilitated by the interstitial voids between the particles. Modification of the TiO2 surface by CsBr further strengthens its interaction with the perovskite. As a result, photogenerated electrons are extracted rapidly producing a very high fill factor of close to 80% a VOC of 1.14 V and a PCE up to 21% with negligible hysteresis.  相似文献   

6.
    
Perovskite solar cells (PSCs) are considered one of the most promising next‐generation examples of high‐tech photovoltaic energy converters, as they possess an unprecedented power conversion efficiency with low cost. A typical high‐performance PSC generally contains a perovskite active layer sandwiched between an electron‐transport layer (ETL) and a hole‐transport layer (HTL). The ETL and HTL contribute to the charge extraction in the PSC. However, these additional two layers complicate the manufacturing process and raise the cost. To extend this technology for commercialization, it is highly desired that the structure of PSCs is further simplified without sacrificing their photovoltaic performances. Thus, ETL‐free or/and HTL‐free PSCs are developed and attract more and more interest. Herein, the commonly used methods in reducing the defect density and optimizing the energy levels in conventional PSCs in order to simplify their structures are summarized. Then, the development of diverse ETL‐free or/and HTL‐free PSCs is discussed, with the PSCs classified, including their working principles, implemented technologies, remaining challenges, and future perspectives. The aim is to redirect the way toward low‐cost and high‐performance PSCs with the simplest possible architecture.  相似文献   

7.
    
In a two-step procedure for fabricating perovskite films, the PbI2 layer formed on the substrate is converted to perovskite by reacting PbI2 with organic iodide. Excess PbI2 left after forming perovskite composition, however, might have an ill effect on device stability and current–voltage hysteresis, although it positively affects efficiency improvement.  Additive engineering is reported here on to control the residual PbI2 in a two-step procedure. A series of organic multi-ammonium chloride derivatives are introduced into the PbI2 precursor solution for the first-step coating, which results in an increase in the perovskite grain size. In addition, carrier lifetime is elongated due to the reduced trap density and the energetics are adjusted to facilitate the extraction of photogenerated carriers. The aminoguanidinium-containing precursor leads to an improved power conversion efficiency (PCE) as compared to the bare PbI2 precursor mainly due to the significantly enhanced open-circuit voltage and fill factor. Consequently, a PCE of 23.46% is achieved from the hysteresis-less photovoltaic parameters and 93% of the initial PCE is maintained after aging for 1000 h in ambient conditions.  相似文献   

8.
    
All-inorganic perovskite solar cells (PSCs) have been the research focus due to their high thermal stability and proper band gap for tandem solar cells. However, their power conversion efficiency (PCE) is still lower than that of organic-inorganic hybrid PSCs. Herein, a sacrificing dye (Rhodamine B isothiocyanate, RBITC) is developed to regulate the growth of perovskite film by in situ release of ethylammonium cations, isothiocyanate anions and benzoic acid molecules upon annealing and illumination. The ethylammonium cations can efficiently passivate surface defects. The isothiocyanate anions incorporate with uncoordinated Pb to regulate the crystallization process. The benzoic acid molecules facilitate the nucleation of the perovskite crystals. Especially, the illumination can accelerate the release of these beneficial ions/molecules to improve the quality of perovskite films further. After optimization with RBITC, a high open circuit voltage (VOC) of 1.24 V and a champion PCE of 20.95% are obtained, which are among the highest Voc and PCE values of CsPbI3 PSCs. Accordingly, the operational stability of the PSC devices is significantly improved. The results provide an efficient chemical strategy to regulate the formation of perovskite films in whole crystallization process for high performance all-inorganic PSCs.  相似文献   

9.
    
Tin oxide (SnO2) is currently the dominating electron transport material (ETL) used in state-of-the-art perovskite solar cells (PSCs). However, there are amounts of defects distributed at the interface between ETL and perovskite to deteriorate PSC performance. Herein, a molecule bridging layer is built by incorporating 2,5-dichloroterephthalic acid (DCTPA) into the interface between the SnO2 and perovskites to achieve better energy level alignment and superior interfacial contact. The multifunctional molecular bridging layer not only can passivate the trap states of Sn dangling bonds and oxygen vacancies resulting in improved conductivity and the electron extraction of SnO2 but also can regulate the perovskite crystal growth and reduce defect-assisted nonradiative recombination due to its strong interaction with undercoordinated lead ions. As a result, the DCTPA-modified PSCs achieve champion power conversion efficiencies (PCEs) of 23.25% and 20.23% for an active area of 0.15 cm2 device and 17.52 cm2 mini-module, respectively. Moreover, the perovskite films and PSCs based on DCTPA modification show excellent long-term stability. The unencapsulated target device can maintain over 90% of the initial PCE after 1000 h under ambient air. This strategy guides design methods of molecule bridging layer at the interface between SnO2 and perovskite to improve the performance of PSCs .  相似文献   

10.
    
Passivating surface defects on perovskite films with tailored functional materials has emerged as one of the most effective strategies for achieving high-performance perovskite solar cells (PSCs). Among existing material selections, potassium salts stand out for their effective passivation of defects surrounding perovskite grain boundaries. However, the widely used potassium salts are inorganic and only soluble in highly polar solvents, which limits their practical application for surface passivation. Herein, a novel organic potassium salt (KCFSO), with multiple organic functional groups and good solubility in low polar isopropanol, is reported to function as a post-treatment agent for perovskite. Combined with experimental results and theoretical calculations, the formed multiple intermolecular interactions between KCFSO and perovskite are revealed to play a vital role in determining the defect passivation effect. Thus, the KCFSO-modified film shows a more uniform surface potential distribution, dramatically decreased defect density, and improved charge transfer, leading to a champion power conversion efficiency (PCE) of 25.11%, and good stability for the derived PSCs. As a demonstration of scalability, the centimeter-sized PSCs and 5 cm × 5 cm mini-modules also demonstrate impressive PCEs of 24.17% and 20.18%, respectively. These findings provide insights into passivator design principles to achieve efficient and stable perovskite photovoltaics.  相似文献   

11.
    
Chemical doping of organic semiconductors enables significant progress in improving their optoelectronic performance. However, the correlation between doping counter ions and charge-transport mechanism has not been yet well-understood. In this study, it is discovered that the anion-dependent degree of delocalization (DOD) of lithium-based dopants significantly determines the doping kinetics as well as the conductivity of organic hole transport layer (HTL), leading to large variation in solar cell efficiency and device stability. Specifically, the incorporation of bis(pentafluoroethanesulfonyl) imide (PFSI−) as the anion with a high DOD results in one order of magnitude higher film conductivity and thus an elevated power conversion efficiency (PCE) exceeding 22.1%, much higher than the state-of-the-art lithium bis(trifluoromethane)sulfonimide (LiTFSI) (21.1%) and lithium hexafluorophosphate (LiPF6) (20.0%). Moreover, the dopant LiPF6 with a smaller DOD produces higher doping yield of HTL accompanied by stronger light-induced PCE fluctuation. Structural analysis reveals anion-modulated ion exchange kinetics determine the hole-transport mechanism and device photostability. To mitigate these detrimental effects, a versatile strategy of Li+ solvation is developed to modulate the anion dissociation, enabling simultaneous improvement of device efficiency and stability. This study elucidates an intriguing and generally applicable doping mechanism, and envisages a bright future to further developing efficient and stable organic electronics.  相似文献   

12.
    
Halide perovskites are one of the ideal photovoltaic materials for constructing flexible solar devices due to relatively high efficiencies for low‐temperature solution‐processed devices. However, the overwhelming majority of flexible perovskite solar cells are produced using spin coating, which represents a major hurdle for upscaling. Here, a scalable approach is reported to fabricate efficient and robust flexible perovskite solar cells on a polymer substrate. Thiourea is introduced into perovskite precursor solution to modulate the crystal growth, resulting in dense and uniform perovskite thin films on rough surfaces. As a decisive step, a cascade energy alignment is realized for the hole extraction layer by rationally designing a bilayer interface comprised of PEDOT:PSS/PTAA with a distinct offset in the highest occupied molecular orbital levels, enabling markedly enhanced charge extraction and spectral response. An efficiency as high as 19.41% and a record fill factor up to 81% are achieved for flexible perovskite devices processed by a scalable printing method. Equally important, the bilayer interface reinforces the bendability of the indium tin oxide substrate, leading to enhanced mechanical robustness of the flexible devices. These results underpin the importance of morphology control and interface design in constructing high‐performance flexible perovskite solar cells.  相似文献   

13.
    
Perovskite solar cells promise to reach the highest efficiencies at the lowest costs, but the mobile ions create challenges in both cell measurements and performance improvement. Being able to understand the ion migration mechanism and its impacts would help to solve relevant issues and may open up opportunities for further development. Although some efforts have been made here, explanations are often too exotic resulting in not only some controversies but the neglect of some important aspects addressable by familiar concepts. This paper uses familiar knowledge in solar cell device physics to explain the ion migration mechanism and its impacts under conditions of interests. It is shown that, when depletion layers contract such as in a forward current‐voltage scan, tardy ionic charges can distort the perovskite bands hence reduce the net currents before they move to new equilibriums, causing the hysteresis effect. As ion migration impacts the electron and hole distributions, it can affect the Shockley‐Read‐Hall and Auger processes differently, hence may either reduce or increase the ratio of radiative to nonradiative recombination. This previously unaddressed mechanism for variation in the electron‐hole recombination can explain photoluminescence quenching and enhancement as well as performance degradation and improvement during ion migration.  相似文献   

14.
    
Facile electron injection and extraction are two key attributes desired in electron transporting layers to enhance the efficiency of planar perovskite solar cells. Herein it is demonstrated that the incorporation of alkali metal dopants in mesoporous TiO2 can effectively modulate electronic conductivity and improve the charge extraction process by counterbalancing oxygen vacancies acting as nonradiative recombination centers. Moreover, sulfate bridges (SO42?) grafted on the surface of K‐doped mesoporous titania provide a seamless integration of absorber and electron‐transporting layers that accelerate overall transport kinetics. Potassium doping markedly influences the nucleation of the perovskite layer to produce highly dense films with facetted crystallites. Solar cells made from K:TiO2 electrodes exhibit power conversion efficiencies up to 21.1% with small hysteresis despite all solution coating processes conducted under ambient air conditions (controlled humidity: 25–35%). The higher device efficiencies are attributed to intrinsically tuned electronic conductivity and chemical modification of grain boundaries enabling uniform coverage of perovskite films with large grain size.  相似文献   

15.
    
Metal halide perovskite single crystals are promising for photovoltaic applications due to their outstanding properties. However, the high surface trap density causes severe nonradiative recombination and ion migration, hindering device performance and stability. Herein, mitigation of the deficient crystal surface is reported by optimized polishing engineering, resulting in stoichiometric lead-iodine ratio with reduced iodide ion vacancies, increased ion migration activation energy, and suppressed nonradiative recombination. As a result, Cs0.05FA0.95PbI3 (FA = formamidinium) devices exhibit an impressive efficiency of 23.1%, which is one of the highest values for single-crystal perovskite solar cells (PSCs). Moreover, multiple recycling of the degraded single-crystal PSCs with higher efficiency and stability is achieved by removing the deteriorated surface, validating crystal surface dominates device degradation while the role of bulk and buried interface is negligible, which is different from polycrystalline devices. The T85 lifetime (remain 85% of initial efficiency) of Cs0.05FA0.95PbI3 devices increases to 1150 h after the recycling process, which is much better than that of previously reported single-crystal PSCs. Since deficient crystal surface and ion migration are universal issues of perovskite materials, this work will promote the development of stable single-crystal PSCs and other optoelectronic devices, such as X-ray detectors, light-emitting diodes, etc.  相似文献   

16.
    
Gapless interdigitated back contact (IBC) solar cells were fabricated with phosphorous back surface field on a boron emitter, using an ion implantation process. Boron emitter (boron ion implantation) is counter doped by the phosphorus back surface field (BSF) (phosphorus ion implantation) without gap. The gapless process step between the emitter and BSF was compared to existing IBC solar cell with gaps between emitters and BSFs obtained using diffusion processes. We optimized the doping process in the phosphorous BSF and boron emitter region, and the implied Voc and contact resistance relationship of the phosphorous and boron implantation dose in the counter doped region was analyzed. We confirmed the shunt resistance of the gapless IBC solar cells and the possibility of shunt behavior in gapless IBC solar cells. The highly doped counter doped BSF led to a controlled junction breakdown at high reverse bias voltages of around 7.5 V. After the doping region was optimized with the counter doped BSF and emitter, a large‐area (5 inch pseudo square) gapless IBC solar cell with a power conversion efficiency of 22.9% was made.  相似文献   

17.
         下载免费PDF全文
Defects as non-radiative recombination centers hinder the further efficiency improvements of perovskite solar cells (PSCs). Additive engineering has been demonstrated to be an effective method for defect passivation in perovskite films. Here, we employed (4-methoxyphenyl) potassium trifluoroborate (C7H7BF3KO) with begin{document}${{rm{BF}}_3^-}$end{document} and K+ functional groups to passivate spray-coated (FAPbI3)x(MAPbBr3)1–x perovskite and eliminate hysteresis. It is shown that the F of begin{document}${{rm{BF}}_3^-}$end{document} can form hydrogen bonds with the H atom in the amino group of MA+/FA+ ions of perovskite, thus reducing the generation of MA+/FA+ vacancies and improving device efficiency. Meanwhile, K+ and reduced MA+/FA+ vacancies can inhibit ion migration, thereby eliminating hysteresis. With the aid of C7H7BF3KO, we obtained hysteresis-free PSCs with the maximum efficiency of 19.5% by spray-coating in air. Our work demonstrates that additive engineering is promising to improve the performance of spray-coated PSCs.  相似文献   

18.
    
Perovskite solar cells (PSCs) have experienced exceptional development in recent years, due to their outstanding photoelectronic properties and low-cost solution processing. Many state-of-the-art PSC designs have been effectively demonstrated using a stacked 3D perovskite/2D perovskite heterostructure, yet limitations arise due to the low conductivity of the 2D perovskite, the hidden buried interface of 3D perovskite, and halide ion migration within 3D/2D PSC device under operational bias. Here, these limitations are overcome by developing a novel and universal post-synthetic metal (Zn2+) doping strategy and realizing 3D/2D PSCs with superior efficiency and stability. Informed by ab initio calculations and synchrotron fine structure experiments, it is revealed that the introduced zinc ions are energetically favored at interstitial crystal sites, subsequently hindering the migration of halide ions and producing a beneficial shift toward a more n-type character in the buried 3D perovskite interface. Combined with extensive photophysical characterization, the Zn2+-modified 3D/2D perovskite thin film is shown to strongly recover its photo-carrier conductivity compared with the 3D/2D perovskite film, boosting the efficiency (22.90%) of PSCs while exhibiting improved humidity and operational stability.  相似文献   

19.
  相似文献   

20.
    
2D halide perovskites have recently been recognized as a promising avenue in perovskite solar cells (PSCs) in terms of encouraging stability and defect passivation effect. However, the efficiency (less than 15%) of ultrastable 2D Ruddlesden–Popper PSCs still lag far behind their traditional 3D perovskite counterparts. Here, a rationally designed 2D‐3D perovskite stacking‐layered architecture by in situ growing 2D PEA2PbI4 capping layers on top of 3D perovskite film, which drastically improves the stability of PSCs without compromising their high performance, is reported. Such a 2D perovskite capping layer induces larger Fermi‐level splitting in the 2D‐3D perovskite film under light illumination, resulting in an enhanced open‐circuit voltage (Voc) and thus a higher efficiency of 18.51% in the 2D‐3D PSCs. Time‐resolved photoluminescence decay measurements indicate the facilitated hole extraction in the 2D‐3D stacking‐layered perovskite films, which is ascribed to the optimized energy band alignment and reduced nonradiative recombination at the subgap states. Benefiting from the high moisture resistivity as well as suppressed ion migration of the 2D perovskite, the 2D‐3D PSCs show significantly improved long‐term stability, retaining nearly 90% of the initial power conversion efficiency after 1000 h exposure in the ambient conditions with a high relative humidity level of 60 ± 10%.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号